The reliable use of ceramics as structural components requires effective means for detection of defects in the material in order to evaluate the possibility of material failure. For example, the lifetime of ceramic components can be affected by cracks, porosity, and foreign inclusions. Furthermore, many fractures originate near the surface, indicating that surface defects such as cracks or small cavities can be an important source of such failures. The critical size of cracks or pores which may lead to fracture can be relatively small in ceramic parts as compared with metal parts. A variety of nondestructive evaluation methods are used to probe for the presence of small defects in materials including microfocus x-radiography, microwave nondestructive evaluation, acoustic surface wave testing, photo-acoustic microscopy, acoustic emission detection, and high frequency ultrasonic testing.
Examination of tubing, in particular, can be a demanding task due to the possibility of extensive lengths to be examined and the difficulty of examining inner-tubular areas which have poor accessibility. Currently, tubular members are examined ultrasonically in one of three ways:
(1) by the passing of an ultrasonic transducer through the tube and detecting and analyzing the transmitted or reflected ultrasonic signals (see K. J. Longua, G. K. Whitman, and J. T. McElroy, Matl. Eval., 54 (1977);
(2) by the mounting of the tubular member on a lathe or related device, translating and rotating the tubing about a fixed transducer, and detecting and analyzing the signals from the transducer (see K. V. Cook and R. A. Cunningham, Jr., ORNL/TM-7373 (1980); or
(3) by the driving of a turbine with a flowing stream of water, with the turbine containing an ultrasonic transmitter and receiver (see H. H. Neely and H. L. Renger, Am. Soc. Non-Destructive Testing, National Fall Conference, p. 275, St. Louis, Mo., Oct. 1979).
The first method is extremely tedious and time consuming to carry out since a large set of linear scans is required to examine the entire tubing. In the second method, the movement of the tubular member is inconvenient at best and at worst can be impossible if the tubing is fixed in place. In the last method it is possible to carry out a circumferential and linear scan without rotating and translating the entire probe package, but the circumferential scan is dependent on fluid flow turning a turbine which contains the probe. Dependence upon fluid flow dictates sharp limitations on the probe capabilities, such as scan speed and even the feasibility of using such a scheme if the test conditions make it impossible to induce the flow of fluid through the tube to be examined.
It is therefore an object of the invention to provide a device for the complete ultrasonic scanning examination for defects in test materials.
It is also an object of the invention to provide a device of integral structure having one or more rotating and scanning ultrasonic mirrors which permit rapid, complete ultrasonic examinations for defects in tubular materials.
It is a further object of the invention to provide an ultrasonic probe device having two motor driven rotating and scanning ultrasonic mirrors which simultaneously analyze for circumferential, longitudinal, or transverse defects from within a tubular material.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.